An optical transmission technology tends to develop towards single-channel with a higher rate (for example, single-channel with 400G/1T), higher spectral efficiency and high-order modulation format, and continuing increasing rate is thus still the most definite and important direction of development of optical transmission. There are many limits to high-speed transmission, mainly including two aspects: on one hand, the optical transmission technology develops towards high-spectral efficiency convergence transmission and high-speed service interface transmission, convergence of low speed to high speed for transmission is insignificant if spectral efficiency cannot be continuously improved, but it is also necessary to consider problems about transmission of a high-speed interface because there may be a high-speed Ethernet interface on a client side, and 400G may be a critical point of a spectral efficiency limit in the future; and on the other hand, the optical transmission technology develops towards long-distance (long-span and multi-span) transmission, and although a system OS to Noise Ratio (OSNR) may be increased by means of adopting a low-loss optical fibre, adopting a low-noise amplifier, reducing a span spacing and the like, achieved improvements are limited, and it is difficult to achieve a major breakthrough and implement a project.
Along with increase of bearer network bandwidth requirements, a beyond-100G technology becomes a solution to increasing bandwidth requirements, and for no matter 400G or 1T beyond 100G, it is impossible for traditional 50 GHz fixed grid Wavelength Division Multiplexing (WDM) to provide a sufficient spectral width for implementation of the beyond-100G technology. Because of defects of a fixed grid, a requirement on a wider flexible grid is made.
In the related technology, beyond-100G multi-rate mixed transmission and beyond-100G modulation format flexibility cause different channel bandwidth requirements, and if each channel is customized with a proper bandwidth, a system bandwidth may be fully utilized, thereby generating a flexible grid system. A requirement on an ultrahigh-speed WDM system continuously increases on the basis of a bandwidth requirement, so that a requirement on a flexible grid technology is introduced. However, many problems such as how to effectively implement frequency spectrum planning and management and achieve compatibility with an existing system are to be solved.
For the problem of how to effectively implement frequency spectrum planning and management, for example, how to break a limit to a selected fixed rate under a beyond-100G condition, after introduction of a flexible grid technology in the related technology, there is yet no effective solution.